CN115103971A

CN115103971A - Limited slip differential and control method thereof

Info

Publication number: CN115103971A
Application number: CN202180014114.XA
Authority: CN
Inventors: 李炯一
Original assignee: Hyundai Wia Corp
Current assignee: Hyundai Wia Corp
Priority date: 2020-02-12
Filing date: 2021-02-05
Publication date: 2022-09-23
Also published as: KR102337224B1; WO2021162360A1; DE112021000976T5; KR20210102655A; US20230068948A1

Abstract

The present invention relates to a technique for continuously performing a transition between a medium torque transmission state and a high torque transmission state through a limited slip differential during running of a vehicle. The invention provides a limited slip differential and a control method thereof, wherein the limited slip differential is configured to comprise: the differential mechanism comprises an input shaft, an output shaft, a medium torque transmission device and a high torque transmission device, wherein the input shaft is always connected to a differential case of the differential mechanism; the output shaft is selectively connected to the input shaft through a clutch plate set and is always connected to the wheels; the intermediate torque transmitting device is used for pressing a clutch plate coupled to the input shaft so as to press fit a clutch plate set; the high torque transmitting device is selectively engaged with the clutch plates by moving a hub coupled to the output shaft in a state where the input shaft and the output shaft are synchronized as the clutch plate pack is tightened.

Description

Limited slip differential and control method thereof

Technical Field

The invention relates to a limited slip differential and a control method thereof, wherein switching between a medium torque transmission state and a high torque transmission state is continuously realized through the limited slip differential during the running of a vehicle.

Background

A differential means a device for generating a speed difference between an inner wheel and an outer wheel when a vehicle turns.

When the wheels of the vehicle enter a low-friction road surface (such as a sand or frozen road surface), the wheels that have entered the low-friction road surface rotate at high speed without traction, and little power is transmitted to the wheels located on a high-friction road surface, making it difficult for the vehicle to be detached from the low-friction road surface.

Meanwhile, a limited slip differential is a device for solving the disadvantages of such a differential, and plays a role in limiting differential motion.

For example, a limited slip differential may be provided between the differential and the wheels, and a multi-plate clutch may be provided between an input shaft connected to the differential case and an output shaft connected to the wheels.

If the multiplate clutch is engaged, torque applied from the input shaft is transmitted to the output shaft through the multiplate clutch, thereby limiting the differential action of the differential.

The torque transmission force transmitted by the multiplate clutch is determined by the disc size of the multiplate clutch, the piston pressure force, and the like, and in order to transmit a high torque of 5000Nm or more, the size of the multiplate clutch and the piston pressure force need to be increased.

Further, in order to increase the pressurizing force, the piston needs to be increased in size, and the pressurizing power source (e.g., a motor or a pump) needs to be increased in size.

However, if the size of the components constituting the limited slip differential is increased, vehicle mountability is reduced, vehicle weight is increased, cost is increased, and other problems make it difficult to apply it to a vehicle.

Meanwhile, Korean laid-open patent publication No.10-2018-0038372 has been proposed as a prior art to solve such problems.

A limited slip differential for a vehicle according to the related art has a screw mechanism configured to convert rotation of an electric motor into linear motion of a side gear shaft of a nut member in a first axial direction.

If the piston mounted on the nut member is moved opposite to the direction in which the frictional engagement element is pressed, the piston and the clutch drum are engaged and become unable to rotate relative to each other, thereby mechanically restricting differential rotation of the pair of side gears.

Therefore, by rotating the single electric motor, the rear wheel differential generates a differential limiting torque for limiting differential rotation of the pair of side gears, or mechanically limits differential rotation of the pair of side gears.

However, the prior art has a problem in that if a state is to be switched from a state in which differential limiting torque is generated to a state in which differential rotation is mechanically limited, the generation of differential limiting torque needs to be cancelled, and differential rotation needs to be limited after parking. In other words, it is very inconvenient to mechanically restrict the differential rotation.

The above description of the background art is only for background help in understanding the present invention and should not be taken as corresponding to the known prior art by a person skilled in the art.

The related prior art includes KR 10-2018 and 0038372A.

Disclosure of Invention

Technical problem to be solved by the invention

The present invention has been made to solve the above-mentioned problems, and an aspect of the present invention provides a limited slip differential and a control method thereof, in which switching between a medium torque transmission state and a high torque transmission state is continuously achieved by the limited slip differential during running of a vehicle.

Technical scheme for solving technical problem

According to one aspect, the invention may comprise: the differential mechanism comprises an input shaft, an output shaft, a medium torque transmission device and a high torque transmission device, wherein the input shaft is always connected to a differential case of the differential mechanism; the output shaft is selectively connected to the input shaft through a clutch plate set and is always connected to the wheels; the intermediate torque transmitting device is configured to press clutch plates coupled to the input shaft such that the clutch plate set is compressed and engaged; a hub coupled to the output shaft is moved by the high torque transmitting device to selectively engage the clutch plates in a state where the input shaft and the output shaft are synchronized according to engagement of the clutch plate sets.

The intermediate torque transmitting means may comprise: a clutch plate provided at an end of the clutch plate group and spline-coupled to an inner circumferential surface of the input shaft to move in an axial direction; and a first piston configured to press the clutch plates in a direction in which the clutch plate groups are engaged.

The high torque transmitting device may include: internal plate teeth, a hub, external hub teeth, and a second piston, the internal plate teeth being formed on the clutch plate; the hub is splined to an outer circumferential surface of the output shaft to move in an axial direction; the hub external teeth are formed on the hub, and the shape of the hub corresponds to the shape of the sheet internal teeth so as to be meshed with the sheet internal teeth; the second piston is configured to press the hub such that the outer hub teeth move to a position where the outer hub teeth mesh with the inner plate teeth.

The in-plate teeth may be formed on an inner peripheral surface of the clutch plate; and the hub external teeth may be formed at an outer circumferential surface of the hub to be spline-coupled to the plate internal teeth.

The output holder may be integrally formed in a cylindrical shape extending in an outer diameter direction from the shaft portion of the output shaft; one end of the hub may be spline-coupled with an outer circumferential surface of an end portion of the output holder; and the other end of the hub may be bent inward to be pressed by the second piston.

A method for controlling operation of a limited slip differential according to the present invention may include: a medium torque transmission step in which, when a medium torque transmission condition required for the limited slip differential according to a vehicle running state is satisfied, the controller performs control such that the clutch plates are pressed to enable the clutch plate group to be compressed and engaged; and a high torque transmission step of, when a high torque transmission condition required by the limited slip differential according to a vehicle running state is satisfied, the controller performing control such that the hub coupled to the output shaft is engaged with the clutch plate in a state where the input shaft and the output shaft are synchronized by the medium torque transmission.

ADVANTAGEOUS EFFECTS OF INVENTION

With the above technical solution to solve the technical problem, the present invention is advantageous in that the differential limiting action of the medium torque level and the differential limiting action of the high torque level can be continuously switched so that the differential-limited transmission torque can be seamlessly connected to the target transmission torque. Therefore, the disengagement performance of the vehicle under road conditions such as rough road and low-friction road can be improved, and the differential limiting action can be switched without separate driver's manipulation by increasing/decreasing the transmission torque, thereby improving the driving convenience.

Drawings

Fig. 1 is a sectional view showing the structure of a limited slip differential according to the present invention.

Fig. 2 shows a state in which the differential action of the limited slip differential of the present invention is released.

FIG. 3 illustrates the differential operating state of the limited slip differential of the present invention at a medium torque level.

FIG. 4 illustrates the differential operating state of the limited slip differential of the present invention at high torque levels.

Fig. 5 to 7 explain various transfer torque behaviors during the differential limiting action according to the present invention.

Fig. 8 explains various transmission torque behaviors during the differential limiting action to which the present invention is not applied.

Detailed Description

Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 1 shows a limited slip differential suitable for use with the present invention, which is mounted on one side of the differential using an inner shaft 20 as the axle.

Referring to the drawings, in view of the construction of a limited slip differential, one end of an inner shaft 20 formed as a solid shaft is connected to one side gear (not shown) within the differential (not shown), and the other end of the inner shaft 20 is connected to a wheel (not shown) of a vehicle through a constant velocity joint.

Further, the input shaft 10 is formed as a hollow shaft to be inserted so as to be relatively rotatable with respect to the inner shaft 20, thus forming a structure that is always connected to the differential case 1 of the differential and rotates together therewith.

Further, the output shaft 30 is formed as a hollow shaft to be inserted so as to be rotatably restrained to the inner shaft 20, and the output shaft 30 and the input shaft 10 are connected through a clutch plate set 40 to be configured to selectively transmit the torque transmitted from the input shaft 10 to the wheels through the output shaft 30.

That is, the output shaft 30 is selectively connected to the input shaft 10 through the clutch plate assembly 40 to form a structure that is always connected to the wheels through the inner shaft 20, thereby selectively transmitting the torque transmitted from the input shaft 10 to the wheels.

According to the above structure, since the clutch plate set 40 is disengaged in the normal running state, power input to the differential is transmitted to the inner shaft 20 through the side gear of the differential, and accordingly, power is transmitted to the wheels of the vehicle through the inner shaft 20.

On the other hand, since the clutch plate group 40 is engaged in a driving state requiring a differential limiting operation, power input to the differential is transmitted to the input shaft 10 through the differential case 1 of the differential, the power transmitted to the input shaft 10 is transmitted to the output shaft 30 through the clutch plate group 40, and then transmitted from the output shaft 30 to the inner shaft 20, and transmitted to the wheels of the vehicle.

Specifically, the present invention includes a medium torque transmitting device configured to press the clutch plates 50 coupled to the input shaft 10 such that the clutch plate pack 40 is compressed and engaged, and a high torque transmitting device through which a hub (hub)70 coupled to the output shaft 30 is moved in a state in which the input shaft 10 and the output shaft 30 are synchronized according to the engagement of the clutch plate pack 40, thereby selectively engaging with the clutch plates 50.

For example, the medium torque is a torque transmittable in a general limited slip differential, and may be a maximum torque that can be achieved in a state where a disc of the clutch plate assembly 40 provided in the limited slip differential is surface-pressed (engaged), and may vary depending on specifications of the clutch plate assembly 40.

The high torque is a torque that is higher than the medium torque by a certain amount or more, and may be a torque that can be achieved in a state where the discs of the clutch plate assembly 40 are mechanically engaged.

For reference, a multiplate clutch is preferably applied to the clutch plate pack 40, but other types of clutch mechanisms having the same or similar torque transfer capacity as a multiplate clutch may also be suitable.

That is, when the limited slip differential requires a medium torque level of torque transmission, the multiplate clutch 40 is engaged using the clutch plates 50 coupled to the input shaft 10 as shown in fig. 3, so that the differential action is limited by the compression engagement force.

When the limited slip differential requires torque transmission of a high torque level, as shown in fig. 4, since the rotations of the input shaft 10 and the output shaft 30 are synchronized by the compression engagement force of the multi-plate clutch 40, the hub 70 coupled to the output shaft 30 is pushed to mechanically engage with the clutch plates 50, and thus, the differential action is limited by the mechanical coupling force between the hub 70 and the clutch plates 50.

As described above, the present invention enables the transition between the medium torque transmitting state and the high torque transmitting state to be continuously performed through the limited slip differential during the driving of the vehicle, thereby improving the rough road disengagement performance of the vehicle and improving the driving convenience.

Referring to fig. 1 to 3, in view of the detailed configuration of the medium torque transmission device, a clutch plate 50 is provided at an end of the clutch plate group 40, and the clutch plate 50 is spline-coupled to an inner circumferential surface of the input shaft 10 to move in an axial direction.

Further, the first piston 60 is configured to press the clutch plates 50 in a direction in which the clutch plate group 40 is engaged.

For example, the input holder 14 is integrally formed in a cylindrical shape extending in the outer diameter direction from one end of the shaft portion 12 of the input shaft 10, and a plurality of drive disks 42 are spline-coupled to the inner peripheral surface of the input holder 14.

Further, the output holder 34 is integrally formed in a cylindrical shape extending from the middle of the shaft portion 32 of the output shaft 30 in the outer diameter direction, a plurality of driven discs 44 are spline-coupled to the outer peripheral surface of the output holder 34, and the driven discs 44 are located between the driving discs 42, thereby constituting the multiplate clutch 40.

Specifically, the clutch plate 50 is spline-coupled to an end portion of the inner peripheral surface of the input holder 14 corresponding to the outer side.

Therefore, the first piston 60 is movably disposed in the axial direction to face the clutch plates 50, so that the first piston 60 presses the clutch plates 50 in the axial direction, thereby compressing and engaging the multiplate clutch 40.

At this time, the first piston 60 is preferably operated using hydraulic pressure, but may be operated by an electric driving force using an actuator. In this case, a mechanical coupling structure is provided between the actuator and the first piston 60 to transmit the driving force.

Further, referring to fig. 1 and 4, in view of the detailed configuration of the high torque transmission device, plate internal teeth 52 are formed on a portion of the clutch plate 50.

Then, the hub 70 is spline-coupled to the outer circumferential surface of the output shaft 30, so that the hub 70 moves in the axial direction.

In addition, hub external teeth 72 are formed on a portion of the hub 70, the shape of which corresponds to the piece internal teeth 52, and the hub external teeth 72 mesh with the piece internal teeth 52.

The hub 70 is configured to be pressed by the second piston 80 so that the hub external teeth 72 can move to a position where they mesh with the in-plate teeth 52.

For example, gear-shaped plate internal teeth 52 are formed along the inner peripheral surface of the clutch plate 50.

Then, the hub 70 is spline-coupled to an end portion of the outer peripheral surface of the output holder 34 formed on the output shaft 30, and gear-shaped hub external teeth 72 are formed along the outer peripheral surface of the end portion of the hub 70 closest to the clutch plates 50.

The second piston 80 is movably disposed in the axial direction to face the hub 70 such that the hub 70 is pushed in the axial direction by the second piston 80, and thus the hub external teeth 72 are moved to positions corresponding to the internal plate teeth 52, so that the hub external teeth 72 are meshed in a spline structure with the internal plate teeth 52.

At this time, the second piston 80 is preferably operated using hydraulic pressure, as with the first piston 60, but may be operated by an electric driving force using an actuator. In this case, a mechanical coupling structure is provided between the actuator and the second piston 80 to transmit the driving force. For reference, although not shown in the drawings, the first and

second pistons

60 and 80 may be moved backward by a return spring.

Referring to fig. 2, the outer circumferential surface of one end of the hub 70 is spline-coupled to the outer circumferential surface of one end of the output holder 34, and the other end of the hub 70 is bent from one end in the inner diameter direction, so that the other end of the hub 70 is pressed by the second piston 80.

For example, when the other end of the hub 70 is bent in the inner diameter direction, the outer face of the other end of the hub 70 is pressed by the second piston 80, and the inner face of the other end of the hub 70 faces the end of the output holder 34.

Therefore, in a state where the hub external teeth 72 and the internal teeth 52 are completely spline-coupled by the hub 70 pressed by the second piston 80, the inner face of the other end of the hub 70 is caught on the end portion of the output retainer 34, and excessive movement of the hub 70 into the multi-plate clutch 40 is suppressed, preventing the multi-plate clutch 40 from being damaged.

The method for controlling the operation of the limited slip differential according to the above-described configuration includes a medium torque transmitting step and a high torque transmitting step.

Referring to fig. 1, first, in the intermediate torque transmission step, when the intermediate torque transmission condition required for the limited slip differential according to the vehicle running state is satisfied, the controller 100 performs control such that the clutch plates 50 are pressed so that the clutch plate group 40 can be compressed and engaged.

For example, when factors reflecting the running state of the vehicle (such as vehicle speed and wheel speed) are detected by the respective sensors and input to the controller 100, the controller 100 analyzes the input values to determine whether or not the intermediate torque transfer condition is satisfied, and as a result of the determination, when it is determined that the intermediate torque transfer condition is satisfied, the controller 100 causes the first piston 60 to operate by the operation of the pressure driving source (pump) 90 to perform a differential limiting action such that the multi-plate clutch 40 is compressed and engaged.

In the high torque transmission step, when a high torque transmission condition required for the limited slip differential according to the driving state of the vehicle is satisfied, the controller 100 performs control such that the hub 70 coupled to the output shaft 30 is engaged with the clutch plate 50 in a state where the input shaft 10 and the output shaft 30 are synchronized through intermediate torque transmission.

For example, when factors reflecting the running state of the vehicle (such as vehicle speed and wheel speed) are detected by the sensors and input to the controller 100, the controller 100 analyzes the input values to determine whether a high torque transmission condition is satisfied, and as a result of the determination, upon determining that the high torque transmission condition is satisfied, the controller 100 causes the second piston 80 to operate by operation of the pressure drive source (pump) 90 to perform a differential limiting action so that the hub 70 is moved, thereby mechanically spline-coupling the hub external teeth 72 with the sheet internal teeth.

For reference, the controller 100 according to an embodiment of the present invention may be implemented by a non-volatile memory (not shown) configured to store data related to an algorithm configured to control operations of various elements of the vehicle or software instructions for reproducing the algorithm, and a processor (not shown) configured to perform the following operations using the data stored in the respective memories. In this case, the memory and the processor may be implemented as separate chips. Alternatively, the memory and the processor may be implemented as a single chip integrated with each other. The processor may have one or more processors.

Taking the operation processes of medium torque transmission and high torque transmission of the limited slip differential as an example, as shown in fig. 2, in the state where the differential limiting action is released, when the limited slip differential requires limiting the differential limiting action to a medium torque level, as shown in fig. 3, the first piston 60 is hydraulically operated to compress and engage the multi-plate clutch 40.

Therefore, the differential action is limited to an intermediate torque level (e.g., 2300Nm) by the compression engagement force of the multi-plate clutch 40.

As shown in fig. 4, in a state where the differential limiting action is limited to the intermediate torque level as described above, when it is required to limit the differential limiting action to the high torque level, the second piston 80 is operated using hydraulic pressure to push the hub 70 toward the clutch plates 50, so the hub external teeth 72 are spline-coupled with the plate internal teeth 52.

That is, since the rotations of the input shaft 10 and the output shaft 30 are synchronized by the compressive engaging force of the multi-plate clutch 40 before the hub external teeth 72 are meshed with the plate internal teeth 52, the hub external teeth 72 naturally move to the plate internal teeth 52 to be meshed therewith.

Thus, differential action is limited to high torque levels (e.g., 5000Nm or more) by the mechanical coupling force between the hub 70 and the clutch plates 50.

Fig. 5 shows the transmitted torque behavior during the differential limiting action according to the invention. Here, since the multi-plate clutch 40 is engaged in a state where the multi-plate clutch 40 is disengaged, the transmission torque gradually increases from the point (i) to the point (ii). At this time, the point corresponding to the state where the multi-plate clutch 40 is fully compressed and engaged is the point at which the differential limiting action is performed by the transmission torque of the intermediate torque level.

Then, when differential limitation of a high torque level is required, the hub 70 is pushed and the hub external teeth 72 mesh with the plate internal teeth 52, and therefore, the transmission torque sharply rises from the point (c) to the point (c). That is, the time point (c) corresponding to the state where the hub 70 and the clutch plate 50 are mechanically engaged with each other is a point at which the differential limiting operation is performed by the transmission torque of the high torque level.

Thereafter, when the differential limitation of the high torque level is maintained until the point (r) is reached while the differential limitation of the medium torque level is required again, the hub 70 is restored and moved so that the hub external teeth 72 meshed with the plate internal teeth 52 are released therefrom, and therefore, the transmission torque sharply decreases from the point (r) to the point (r). However, the point (c) corresponding to the state where the multi-plate clutch 40 is compressed and engaged is a point at which the differential limiting action is still performed by the transmission torque of the intermediate torque level.

When the differential limiting action is not required, the multi-plate clutch 40 is disengaged, and therefore, the transmission torque is gradually reduced from the point (v) to the point (c), and the differential limiting action is completely released at the point (c).

Fig. 6 shows another torque transfer behavior during the differential limiting action according to the invention. Here, when a differential limiting action of an intermediate torque level is required, the multi-plate clutch 40 is engaged, thereby gradually increasing the transmission torque from the point (r).

However, when a differential limiting action of a high torque level is required before the multi-plate clutch 40 is fully engaged, the hub 70 moves during the engagement of the multi-plate clutch 40 so that the hub external teeth 72 mesh with the plate internal teeth 52, and thus the transmission torque sharply rises from point (c) to point (c). Although the torque of point (ii) is smaller than that of the state in which the multi-plate clutch 40 is fully engaged, the torque of point (ii) is a torque level that has no problem in achieving synchronization of the input shaft 10 and the output shaft 30.

That is, when a high torque level differential limiting action is required during a medium torque level differential limiting action, the hub 70 is immediately operated such that the hub 70 is mechanically coupled to the clutch plates 50, thereby performing the differential limiting action at the high torque level.

Fig. 7 shows another torque transfer behavior during the differential limiting action according to the invention. Here, when a differential limiting operation at a medium torque level or less is required in a differential limiting operation at a high torque level, the hub 70 is restored and moved so that the hub outer teeth 72 meshing with the plate inner teeth 52 are released therefrom, and at the same time, a part of the engagement force of the multi-plate clutch 40 is released, so that the transmission torque abruptly drops from point (r) to point (c').

Then, the engagement force of the multi-plate clutch 40 is completely released, so that the transmission torque gradually decreases from point (c) to point (c), and the differential limiting action is completely released at point (c).

That is, when a differential limiting action slightly lower than the intermediate torque level is required in a state where the differential limiting action is performed at a high torque level, only a portion of the engagement force of the multi-plate clutch 40 is released after the mechanical coupling between the hub 70 and the clutch plates 50 is released, and thus, the differential limiting action is performed at a level slightly lower than the intermediate torque level.

Fig. 8 shows the transmission torque behavior when the differential limiting action of the intermediate torque level and the differential limiting action of the high torque level are not continuously performed. Here, after the differential limiting action of the intermediate torque level, the corresponding intermediate torque differential limiting action is released. Then, after the vehicle is stopped, the differential limiting action of the high torque level is performed again.

That is, when the differential limiting operation of the intermediate torque level and the differential limiting operation of the high torque level are not continuously performed, the differential limiting operation cannot be smoothly performed.

As described above, the present invention is able to continuously switch between the differential limiting action of the intermediate torque level and the differential limiting action of the high torque level, so that it is possible to connect the differential-limited transmission torque seamlessly to the target transmission torque.

Therefore, the present invention improves the disengagement performance of the vehicle under road conditions such as rough road and low friction road, and is able to switch the differential limiting action according to an increase or decrease in the transmission torque without the driver's separate manipulation, thereby improving the driving convenience of the driver.

Although the present invention has been described in detail with respect to only the above specific examples, it is apparent to those skilled in the art that various modifications and variations can be made within the technical spirit of the present invention, and such changes and modifications are within the scope of the appended claims.

Description of reference numerals:

1: differential case

10: input shaft

12: shaft part

14: input holder

20: inner shaft

30: output shaft

32: shaft part

34: output keeper

40: clutch disc set (Multi-plate clutch)

42: driving disc

44: driven plate

50: clutch disc

52: in-sheet tooth

60: first piston

70: hub

72: external gear of hub

80: second piston

90: pressure driving source

100: and a controller.

Claims

1. A limited slip differential, comprising:

an input shaft always connected to a differential case of a differential;

an output shaft selectively connected to the input shaft through a clutch plate set and always connected to a wheel;

a medium torque transmitting device configured to press clutch plates coupled to an input shaft such that the clutch plate set is compressed and engaged; and

a high torque transfer device through which a hub coupled to the output shaft is moved to selectively engage the clutch plates in a state in which the input shaft and the output shaft are synchronized according to engagement of the clutch plate sets.

2. The limited slip differential according to claim 1, wherein the intermediate torque transmitting device comprises:

a clutch plate provided at an end of the clutch plate group and spline-coupled to an inner circumferential surface of the input shaft to move in an axial direction; and

a first piston configured to press the clutch plates in a direction in which the clutch plate groups engage.

3. The limited slip differential according to claim 1, wherein the high torque transmitting device comprises:

inner plate teeth formed on the clutch plate;

a hub spline-coupled to an outer circumferential surface of the output shaft to move in an axial direction;

hub external teeth formed on the hub, having a shape corresponding to the sheet internal teeth, to be engaged with the sheet internal teeth; and

a second piston configured to press the hub such that the hub outer teeth move to a position where the hub outer teeth mesh with the plate inner teeth.

4. The limited slip differential according to claim 3, wherein the in-plate teeth are formed on an inner peripheral surface of the clutch plate;

the hub external teeth are formed on an outer circumferential surface of the hub to be spline-coupled to the in-plate teeth.

5. The limited slip differential according to claim 3, wherein the output retainer is integrally formed in a cylindrical shape extending in an outer diameter direction from the shaft portion of the output shaft;

one end of the hub is spline-coupled with an outer circumferential surface of an end portion of the output holder;

the other end of the hub is bent inward to be pressed by the second piston.

6. A method for controlling operation of the limited slip differential of claim 1, the method comprising:

a medium torque transmission step in which, when a medium torque transmission condition required for the limited slip differential according to a vehicle running state is satisfied, the controller performs control such that the clutch plates are pressed to enable the clutch plate group to be compressed and engaged; and

a high torque transmission step of, when a high torque transmission condition required by the limited slip differential according to a vehicle driving state is satisfied, controlling a hub coupled to the output shaft to be engaged with the clutch plates in a state where the input shaft and the output shaft are synchronized by the medium torque transmission.